f91ca31f53
commit 3c4276936f6fbe52884b4ea4e6cc120b890a0f9f upstream.
We recently ran into the following deadlock involving
btrfs_write_inode():
[ +0.005066] __schedule+0x38e/0x8c0
[ +0.007144] schedule+0x36/0x80
[ +0.006447] bit_wait+0x11/0x60
[ +0.006446] __wait_on_bit+0xbe/0x110
[ +0.007487] ? bit_wait_io+0x60/0x60
[ +0.007319] __inode_wait_for_writeback+0x96/0xc0
[ +0.009568] ? autoremove_wake_function+0x40/0x40
[ +0.009565] inode_wait_for_writeback+0x21/0x30
[ +0.009224] evict+0xb0/0x190
[ +0.006099] iput+0x1a8/0x210
[ +0.006103] btrfs_run_delayed_iputs+0x73/0xc0
[ +0.009047] btrfs_commit_transaction+0x799/0x8c0
[ +0.009567] btrfs_write_inode+0x81/0xb0
[ +0.008008] __writeback_single_inode+0x267/0x320
[ +0.009569] writeback_sb_inodes+0x25b/0x4e0
[ +0.008702] wb_writeback+0x102/0x2d0
[ +0.007487] wb_workfn+0xa4/0x310
[ +0.006794] ? wb_workfn+0xa4/0x310
[ +0.007143] process_one_work+0x150/0x410
[ +0.008179] worker_thread+0x6d/0x520
[ +0.007490] kthread+0x12c/0x160
[ +0.006620] ? put_pwq_unlocked+0x80/0x80
[ +0.008185] ? kthread_park+0xa0/0xa0
[ +0.007484] ? do_syscall_64+0x53/0x150
[ +0.007837] ret_from_fork+0x29/0x40
Writeback calls:
btrfs_write_inode
btrfs_commit_transaction
btrfs_run_delayed_iputs
If iput() is called on that same inode, evict() will wait for writeback
forever.
btrfs_write_inode() was originally added way back in 4730a4bc5bf3
("btrfs_dirty_inode") to support O_SYNC writes. However, ->write_inode()
hasn't been used for O_SYNC since 148f948ba877 ("vfs: Introduce new
helpers for syncing after writing to O_SYNC file or IS_SYNC inode"), so
btrfs_write_inode() is actually unnecessary (and leads to a bunch of
unnecessary commits). Get rid of it, which also gets rid of the
deadlock.
CC: stable@vger.kernel.org # 3.2+
Signed-off-by: Josef Bacik <jbacik@fb.com>
[Omar: new commit message]
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.